Electrical relay



March 18, 1930. s wo ET AL 1,750,658

ELECTRICAL RELAY Filed Sept. 30, 1929 INVENTORSI H, E ir hworth,

B Ldz/Ch,

Qn-W m m ature upon the time constants of a relay.

Patented Mar. 18, 1930 UNITED STATES PATENT} QFFICE HARRY E. ASHWORTH AND BRANKO LAZICH, 0F PITTSBURGH, PENNSYLVANIA, AS-

SIGNORS TO THE UNION SWITCH & SIGNAL COMEANY, 0F SWISSVALE, PENNSYL VANIA, A. CORPORATION OF PENNSYLVANIA ELECTRICAL RELAY Application filed September 30, 1929. Serial No. 396,225.

Our invention relates to electrical relays. One object of our invention is the provision of means for automatically compensating for the effects of changes in the ambient temper- We will describe one form of relay embodying our invention, and will then point out the novel features thereof in claims.

The accompanying drawing is a view, partly diagrammatic, illustrating in isometric projection one form of an electrical relay embodying our invention.

Referring to the drawing, the reference character A designates an electromagnet which, in the form here shown, comprises three magnetizable cores 1, 2 and 3, connected together at their upper ends by a back strap 4, and provided at their lower ends with enlarged pole pieces 1, 2 and 3*, respectively. The core 1 carries an energizing winding 5, and the core 3 carries a similar energizing winding 6. The pole piece 2 is bifurcated, and a magnetizable armature 7 is pivotally supported between the bifurcations of the pole piece 2*, for swinging motion toward one or the other of the pole pieces 1 or 3. Attached to the underside of the armature 7 by means of suitable insulating supports 8,. only one of which is shown in the drawing, are two contact fingers 9 and 10. When armature 7 is swung toward pole piece 3*, as shown in the drawing, contact finger 9 engages a fixed contact member 9 to close a contact 99, and contact finger then en-, gages a fixed contact member 10 to close a contact 1010. When armature 7 is swung trolled in any suitable manner, such as by a manually operable switch 16.

As shown in the drawing, switch 16 is open and armature 7 is swung toward the pole piece 3 so that contacts 99 and 101O are closed. If, now, switch 16 is closed, current flows through winding 5, but since contact 99 is closed, windin 6 is short-circuited, and winding 6 there ore remains deenergi'zed. The energization' of winding 5 sets up a flux in core '1 which causes armature 7 to swing toward pole piece 1*. During this motion of the armature, however, contact 99 'opensand cont-act 9-4) closes. The closing of contact 99 short-circuits winding 5, and the field set up in core 1 by this winding commences to decay. Due, however, to the short-circuited winding, this decay is comparatively slow. The -opening of contact 99 in the meantime has allowed wind ing 6 to become energized. The growth of the field set up in core 3 by current in this latter winding is comparatively rapid and, after a time, the torque exerted on armature 7 by the decreasing flux in core 1 will be overbalanced by the torque exerted on armature 7 by the flux in core 3, so that armature 7 swings toward pole piece 3 This motion will first open contact 99 and then close contact 99. The field of winding 5 will then rapidly build up and the field of winding 6 will slowly decay, this decay being retarded by the inductance of winding 6'. Eventually the torque exerted by the flux in core 3 will not be suflicient to hold the armature, and the armature will then again toward pole Ipziiece 1, however, contact finger swing toward the pole piece 1*. It will,

9 engages a ed contact member 9 to close a contact 9-9", while'contact finger 10 engages a fixed contact member 10 to close .a contact 1010-. l

The windings 5 and 6 of relay A. are con-' nected in series and are supplied with current from a suitable source of energy, here shown as a battery 15, It will be seen from an inspection of the drawing, however, that when contact 99 is closed, winding 6 is short-circuited; and that when contact 99" is closed, winding 5 is short-circuited. The

supply of current to the relay may be contherefore, be apparent that armature 7 is swung to and fro as long as switch 16 is closed and it will also be clear that a considerable time interval elapses between armature movements.

In a relay of the type described, the time interval which elapses between successive armature movements is substantially independent of fluctuations in the electromotive forceof the energy supply because the armature is acted upon by two opposing forces, both of which increase or decrease as the electromotive force of the'energy supply increases or decreases. If .the ambienttemperature increases, however, the impedances of the windthis increase may be prevented byconnecting the pole pieces of the electromagnet by an auxiliary magnetic path, the reluctance of which is increased as the temperature increases.- As here shown, this path comprises a magnetizable shunting member 11, pivotally supported on a pin 17 carried by a downwardly extending projection of one of the bifurcations of the pole piece 2*, and arranged to swing toward or away from the pole pieces 1*,

2 and'3 Attached to the member 11 is a device which changes its shape in response to changes in its temperature. As here shown, this device is a bimetallic strip 12, attached intermediate its end to member 11, and arranged in such manner that its free ends 12" and 12 will deflect toward or away from the pole pieces 1 and 3 respectively, according as the ambient temperature increases or decreases. A pin 13 is attached to the pole piece 1 and extends'with some clearance through a hole 11 in the member 11, and a similar pin 14 is attached to the pole piece 3 and extends through a hole 11 in the-member 11. When relay A is operating, the fluxes set up in the cores 1 and 3 exert a force on the member 11 which moves the member 11' to a position in which the ends 12 and 12 of the strip 12 engage the pins 13 and;14, respectively. The

lengths of the pins 13-and 14 are such, and the strip 12 is so arranged, that at a given temperature, preferably the normal operating temperature of the relay, the member 11 is spaced from the pole pieces 1, 2 and 3 by the proper airga to cause the relay armature to operate at t e desired rate. It will be apparent, therefore, that if the ambient temperature increases, the resultant deflection of the bimetallic strip 12 will move the member 11 away from the pole pieces 1*,2 and 3*, thereby increasin the reluctance of the magnetic path including the member 11, and hence increasing the percentage of the total flux set up in the cores 1 and 3 which threads the armature 7, so that thearmature has a tendency to operate more rapidly. If the ambient temperature decreases, however,- the resultant deflection of the bimetallic strip 12 will permit the member 11 to move toward the pole pieces 1*, 2 and 3", thereby decreas :ing the reluctance of the magnetic paths including the member 11, and hence shunting away from the armature 7 a greater percentage of the total flux set up in the cores 1 and 3, so that the armature '4' tends to operate more slowly. The parts are so proportioned that the variations in the reluctance of the magnetic path including the member 11 will compensate for the Variations of the time interval which elapses between successive armature movements as a resultof temperature changes. It will be apparent, therefore, that in a relay constructed in accordance with our invention, thetime interval which elapsesbetween successive armature movements is unaffected by variations i the electromotive force of the energy supply, or by changes in ambienttemperature, and the time interval between successive, armature movements therefore, remains practically constant.

Relays embodying our invention are particularly suitable for, although in no way limited to, use for periodically interrupting an electric circuit in which a constant open or closed time is desired.

Although we have herein shown and described only one form of electrical relay embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and'scope of our invention.

portion of the flux from said electromagnet away from said armature, and means for varying the reluctance of. said path in response to variations inthe ambient tempera ture.

2. In combination, an electromagnet, an armature controlled .by said electromagnet, an auxiliary magnetic path between the pole pieces of'said electromagnet for shunting a portion ofthe flux from saidelectromagnet away from said armature, and means for in-.

creasing the reluctance of said path in re sponse to increases in the ambient temperature.

3. In combination, an electromagnet, an

armature controlled by said electromagnet, a ma netizable shunting member spaced from eac pole piece of said electromagnet by an air gap, and means for varying said air gaps in response to variationsin ambient temperature.

4. In combination an electr magnet, an armature controlled by said electromagnet, a magnet'izable shunting member spaced from each pole piece of said electromagnet by an air, gap, and means for increasing said air gaps in response toincreases in the ambient temperature.

5. In combination, an electromagnet, an armature controlled by said electromagnet, a

. magnetizable shunting member spaced from each pole piece of saidelectromagnet b an air gap, and a device which changes its sliape in response to changes in its temperature for at times varying said air gaps.

6. In combination, an electromagnet, an

armature controlled by said electromagnet,

I a magnetizable shunting member spaced from piece by an air gap for shunting a portion.

of the flux from said electromagnet away from said armature, a bimetallic strip at tached to said member and having one end free to deflect in response to variation in ambient temperature, and a pin attached to one said pole piece and arranged to engage the free end of said strip in such manner that deflection of said strip varies said air gaps.

8. In combination, an electromagnet comprising a first, a second, and a third magnetizable core connected together at their upper ends by a back strap and provided at their lower ends with a first, a second, and a third pole piece, respectively; a first winding on said first core and a second winding on said third core, a magnetizable armature pivotally attached to said second pole piece and arranged to swing toward said first or said third pole piece according as said first or said second windin is energized, a magnetizable v shunting mem er supported for movement toward or away from all of said cores simultaneously, a bimetallic strip which deflects when heated and attached intermediate its ends to said member and arranged in such manner that its free ends will deflect toward or away from said first and third ole pieces respectively according as the am ient temperature increases or decreases, and a first and second pin attached to said first and third pole pieces respectivel and arranged to engage said strip at its ree ends in such manner that deflections of said strip move said member toward or away from said pole pieces according as the ambient temperature decreases or increases.

9. In combinatlon, an electromagnet, an armature controlled by said electromagnet,

net, and means for varying the reluctance of said auxiliary path with variations in temperature in such manner that changes in the 4 time constant of said relay with changes in temperature due to changes in the impedance of said winding are compensated for by the variations in the reluctance of said auxiliary path.

In testimony whereof weaflix our signatures.

HARRY E. ASHWORTH. BRANKO LAZIGH.

an auxiliary magnetic ath between the poles of said electromagnet or shunting a portion of the'flux from said electromagnet away 'from said armature, and means for varying the reluctance of said auxiliary path with variations in ambient temperature in such manner that'changles in the time constant of said relay due to c reluctance of said path.

'10. In combination, an electromagnet prm vided with a winding, an armature controlled anges in ambient temperature are compensated for by the variations in the 

